KR101349777B1 - Back light control apparatus for liquid crystal display - Google Patents

Abstract

The present invention relates to a technique for increasing the color depth of the image displayed on the liquid crystal panel using a backlight in the liquid crystal display device. The present invention, the LED backlight unit for emitting a backlight using the LED on the liquid crystal display on the liquid crystal panel; In order to analyze the luminance of the input image, the luminance analysis unit for extracting the lamp control data bits from the input data, the LEDs on the LED backlight unit is spatially partitioned, and the lamp driving data corresponding to the lamp control data bits are generated It is achieved by an LED driver composed of a lamp lighting control unit which outputs a lighting control signal to the LEDs of the divided region every frame.

Description

BACK LIGHT CONTROL APPARATUS FOR LIQUID CRYSTAL DISPLAY}

1 is a block diagram of a backlight device of a liquid crystal display device according to the prior art.

2 is a block diagram showing an embodiment of a backlight control device of a liquid crystal display according to the present invention.

Figure 3 is a block diagram implementing the LED driver in the BRC method according to the present invention.

4 is a table of lamp lighting control signals according to the present invention;

5 is a detailed circuit diagram of a lamp lighting control unit according to the present invention.

(A)-(g) is a waveform diagram of each part of FIG.

7 is an exemplary view showing that the LED is lit in the BRC method by spatially dividing the LED according to the present invention.

Figure 8 is another exemplary diagram showing that the LED is lit in a BRC manner by partitioning the LED according to the present invention.

9 is a block diagram implementing the LED driver by dithering technique in accordance with the present invention.

10A and 10D are waveform diagrams of an LED lighting control signal time-divided according to the present invention.

11 is an exemplary diagram of an LED lighting control pattern time-divided according to the present invention.

12 is a block diagram of a backlight control device driven in a BRC method and a dithering method according to the present invention.

Figure 13 is an illustration of a pattern that is lit in the BRC method and dithering method in accordance with the present invention.

DESCRIPTION OF THE REFERENCE SYMBOLS

21: system 22: interface unit

23: timing controller 24: gate driver

25 data driver 26 liquid crystal panel

27: DC / DC converter 28: LED drive unit

29: LED backlight unit 31,91,121: luminance analyzer

32,122: lamp lighting control unit 92,123: frequency multiplication unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for increasing the color depth of an image displayed on a liquid crystal panel using a backlight in a liquid crystal display device. In particular, a digital bit is added by driving a backlight employing a light emitting diode in time and space. The present invention relates to a backlight control device of a liquid crystal display device capable of improving color depth without having to.

In general, a backlight unit of a liquid crystal display device is in a trend of miniaturization, thinning, and weight reduction, and according to this trend, a light emitting diode (LED), which is advantageous in power consumption, weight, and brightness, is used instead of the CCFL used in the backlight unit. Proposed.

1 is a block diagram of a backlight device of a liquid crystal display device according to the prior art, and as shown therein, an LED driver 11 for supplying an LED driving signal having a predetermined frequency; An LED backlight 12 driven by the LED driver 11 to irradiate a backlight to the liquid crystal display of the liquid crystal panel 13; The liquid crystal panel 13 is configured to generate an image corresponding to the input data and to display the generated image by the backlight. The operation thereof will be described as follows.

The LED driver 11 processes a signal of a driving frequency (for example, 60 Hz) input from a timing controller of the main PC vision and outputs the signal to the LED backlight 12.

Accordingly, LEDs arranged in a matrix form on the LED backlight 12 are driven by driving signals input from the LED driver 11, and the backlight is irradiated onto the liquid crystal display of the liquid crystal panel 13.

In this case, the liquid crystal panel 13 generates an image according to data input from the timing controller using liquid crystal cells (pixels) arranged in a matrix form, and the generated image is reflected on the screen by the backlight. .

The color depth expressed through each pixel on the liquid crystal panel 13 is usually determined by the transmittance of each pixel and the gray scale expression power by the applied voltage.

Nevertheless, in the conventional liquid crystal display device, the LED backlight is used only for LCD lighting, so that the color depth depends entirely on the digital input bit. Therefore, there is a problem in that cost and side effects occur when the color depth is extended by increasing the digital bit.

Accordingly, a first object of the present invention is to provide a backlight control apparatus for spatially dividing LEDs for backlighting and lighting them by BRC (Backlight Rate Control).

A second object of the present invention is to provide a backlight control apparatus for lighting backlight LEDs by using a lamp dithering method after obtaining a driving frequency divided by a time by increasing a multiple of the backlight driving frequency.

A third object of the present invention is to provide a backlight control apparatus for driving the backlight LED in the BRC method and the dithering method.

According to an aspect of the present invention, a luminance analyzer extracts a data bit for lamp control from input data in order to analyze luminance of an input image; And a lamp lighting control unit for spatially dividing the LEDs on the LED backlight unit, generating lamp driving data by expanding the lamp control data bits, and outputting the lamp driving data as lighting control signals to the LEDs of the corresponding divided area every frame. It is characterized by the configuration.

Another object of the present invention to achieve the above object, and to analyze the brightness of the input image, the brightness analysis unit for extracting the data bits for lamp control from the input data; And multiplying the original lamp driving frequency by a predetermined multiple, and using a multiplied driving frequency to include a frequency multiplier that outputs an LED lighting control signal at a corresponding cycle every frame.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is an overall block diagram of a backlight control apparatus of a liquid crystal display according to the present invention, as shown therein; Liquid crystal panel 26 in which m × n liquid crystal cells Clc are arranged in a matrix type, m data lines D1 to Dm and n gate lines G1 to Gn intersect with each other, and a thin film transistor is formed at an intersection thereof. and; A gate driver 24 for supplying a scan signal to the gate lines G1 to Gn under the control of the timing controller 23; A data driver 25 for supplying data to the data lines D1 to Dm of the liquid crystal panel 26 under the control of the timing controller 23; A timing controller 23 outputting a control signal for controlling the driving of the gate driver 24 and the data driver 25; An interface unit 22 for interfacing the system 21 with the timing controller 23; A DC / DC converter 27 for generating various driving voltages required by the liquid crystal panel 26; An LED driver 28 for spatially dividing the LEDs on the LED backlight unit 29 and lighting them in a BRC manner, or generating a driving frequency divided in time and then lighting them by a lamp dithering technique using the LEDs; The LED backlight unit 29 emits a backlight using the LEDs driven by the LED driver 28 to the liquid crystal display on the liquid crystal panel 26.

FIG. 3 is a block diagram illustrating an example of implementing the LED driver 28 in a BRC scheme. As shown in FIG. 3, a lamp is controlled by data input from the timing controller 23 to analyze luminance of an input image. A luminance analyzer 31 for extracting data bits; The LEDs on the LED backlight unit 29 are spatially divided, and lamp driving data corresponding to the lamp control data bits inputted from the luminance analyzer 31 are generated, and the LEDs of the respective divided regions are used as lighting control signals every frame. The lamp lighting control part 32 to output is comprised.

In addition, FIG. 9 is a block diagram illustrating an example of implementing the LED driver 28 using a dithering technique. As illustrated in FIG. A luminance analyzer 91 for extracting data bits for lamp control; After multiplying the original lamp driving frequency by a predetermined multiple, the multiplier includes a frequency multiplier 92 for outputting an LED lighting control signal at a corresponding period every frame using the multiplied driving frequency.

When described in detail with reference to Figures 4 to 9, 10 to 13 attached to the operation of the present invention configured as described above as follows.

The liquid crystal panel 26 has a structure in which liquid crystal is injected between two glass substrates, and the data lines D1 to Dm and the gate lines G1 to Gn formed on the lower glass substrate are perpendicular to each other. Each pixel on the liquid crystal panel 26 is provided with a pixel electrode to apply a voltage according to image information, and applies an electric field to the liquid crystal layer together with a common voltage applied to the common electrode formed on the second substrate. At this time, the liquid crystal molecules constituting the liquid crystal layer are arranged at a constant angle according to the intensity of the electric field.

However, in the present invention, since the FSC driving method is used, red, green, and blue color filters are not used to display colors on the liquid crystal panel 26.

The graphics processing circuit of the system 21 converts analog data into digital video data RGB and adjusts the resolution and color temperature of the digital video data RGB. The digital video data RGB and the vertical / horizontal synchronization signal and the clock signal output from the system 21 are supplied to the timing controller 23 through the interface unit 22.

The interface unit 22 converts the digital video data into a TTL or CMOS level and transmits the parallel video after compressing and transmitting the TDMS (TDMS) or digital video data (RGB) as serial data. Low voltage differential signaling (LVDS) is used to restore data.

The timing controller 23 uses a vertical / horizontal synchronization signal (Vsync / Hsync) and a clock signal supplied from the system 21 through the interface unit 22 to control the gate driver 24. A data control signal DDC for controlling the GDC and the data driver 24 is generated. In addition, the timing controller 23 samples the digital video data RGB inputted from the system 21 through the interface unit 22, rearranges the data, and supplies the data to the data driver 25.

The data driver 25 converts the digital video data RGB into an analog gamma compensation voltage corresponding to the grayscale value in response to the data control signal DDC from the timing controller 23, and converts the converted analog gamma. The compensation voltage is supplied to the data lines D1 to Dm.

The gate driver 24 sequentially supplies scan pulses to the gate lines G1 to Gn in response to the gate control signal GDC from the timing controller 23 to supply horizontal data to the liquid crystal panel 26. Select the lines.

The DC / DC converter 27 generates the high potential common voltages VDD voltage, VCOM voltage, VGH voltage, and VGL voltage using the power terminal voltage VCC input from the system 21.

For reference, in the above description, the data driver 25 and the gate driver 24 are separately installed with the liquid crystal panel 26. However, in recent years, each of them is directly mounted on the liquid crystal panel 26 by packaging technology. Is in.

Meanwhile, FIG. 3 illustrates an embodiment of the LED driver 28 for spatially dividing the LEDs on the LED backlight unit 29 and lighting them in a BRC manner.

In this case, the luminance analyzer 31 analyzes the luminance of the input image, and 2 bits of the most significant bit (MSB) of the data input from the timing controller 23 are bits for controlling the lamp (LED). (bit) is extracted and output to the lamp lighting control unit 32.

In addition, the lamp lighting controller 32 generates 4bit lamp driving data as shown in FIG. 4 based on the lamp control bit input from the luminance analyzer 31 to turn on the LEDs on the LED backlight unit 29. Outputs a lighting control signal for controlling.

FIG. 5 is a circuit diagram showing an embodiment of the lamp lighting control unit 32. Referring to this, the operation of the lamp lighting control unit 32 will be described in more detail as follows.

The data distributor 51 receives the first and second data a and b of the ramp control bits as shown in FIG. 6A and outputs them by branching them to different output terminals.

Thereafter, the first data a is branched through the buffers BUF51 and BUF52 and synthesized by the synthesizer 52A. As a result, the first data a is expanded into two bits of data 'aa' by the buffers BUF51, BUF52, and the synthesizer 52A as shown in FIG.

In addition, the second data b is directly synthesized with 0 bits in the synthesizer 52B and extended to 2 bits of data 'b0' as shown in FIG.

The expanded first data aa is supplied to one input terminal of the AND gate AD51, and the second data b0 is supplied to one input terminal of the AND gate AD52.

At this time, in sequentially outputting the 4-bit data selection signal SEL to the data selection terminal SEL of the data divider 51, the lower 2 bits are output as '11' as shown in FIG. , Upper 2 bits are output as '00'. The 4-bit data selection signal '0011' is inverted through the inverter I51 and output as '1100' as shown in FIG.

The lower 2 bits '11' of the selection signal SEL are directly supplied to the other input terminal of the AND gate AD52, whereby the second data 'b0' input from the synthesizer 52B is selected and It is supplied to the other input terminal of the OR gate OR51.

Subsequently, the selection signal '11' of the upper two bits inverted through the inverter I51 is supplied to the other input terminal of the AND gate AD51, whereby the first data aa input from the synthesizer 52A is inputted. It is selected and supplied to one input terminal of the next-order OR gate OR51.

The OR gate OR51 synthesizes 2 bits of upper data 'aa' and lower data 'b0' input from the AND gates AD51 and AD52, and outputs 4 bits as shown in FIG. The data 'aab0' is printed.

Through the above process, the lamp control bit is converted into output data OUTPUT of 4 bits. Referring to the table of FIG. 4, the conversion characteristics thereof are as follows.

Each of the ramp control bits is extended to the left and right sides by 1 bit, respectively, and converted into 4 bits of output data OUTPUT. However, when the lower bit value is '0', it is expanded to the right as it is (ex: '00' → '0000', '10' → '1100'), but when it is '1', it is set to '0'. Expand to the right (eg '01' → '0010', '11' → '1110').

As in the above description, when the lower bit value is '1', the reason for extending to the right by replacing the value with '0' is to keep the least significant bit value as '0', thereby allowing at least one or more on the LED backlight 29. This is to turn on the LED.

FIG. 7 illustrates an embodiment in which the backlight LEDs on the LED backlight unit 29 are spatially divided and lit on the LED backlight unit 29 in a BRC (Backlight Rate Control) manner. In other words, in FIG. 7, when the LEDs of the LED backlight unit 29 are arranged in a 4 * 4 structure as an example, the LED lamps of the respective allocation areas according to the lamp control bit are performed by the lamp lighting control unit 32 every frame. An example of selecting and lighting them is shown.

That is, when the lamp control bit is '00' in the first frame, five LEDs located in an arbitrary region are turned on as shown in (a) of FIG. 7, and when the lamp control bit is '01' in the second frame. , 5 LEDs located in another area as shown in (b) of FIG. 7 are turned on, and when the lamp control bit is '10' in the third frame, 3 located in another area as shown in (c) of FIG. LEDs are turned on, and when the lamp control bit is '11' in the fourth frame, three LEDs located in another area are turned on as shown in FIG.

FIG. 8 illustrates another embodiment in which the LEDs for the backlight on the LED backlight unit 29 are spatially divided and turned on in the BRC (Backlight Rate Control) method.

That is, in the first frame, all 16 LEDs are turned on according to the output data '0000', and in the second frame, all the LEDs except one LED are turned on in accordance with the output data '0010'. In the first frame, all the LEDs except for the four LEDs of 16 LEDs are turned on according to the output data '1100', and in the fourth frame, all the LEDs except the nine LEDs of the 16 LEDs are turned on according to the output data '1110'. Lights up.

Meanwhile, FIG. 9 illustrates another embodiment of the LED driver 28 for turning on the LEDs for the backlight by a lamp dithering technique by generating a driving frequency divided in time by increasing a multiple of the backlight driving frequency. .

Here, the luminance analyzer 91, as in the luminance analyzer 31 of FIG. 3, analyzes the luminance of the input image, and includes the most significant bit of data input from the timing controller 23. 2 bits of the MSB are extracted to the lamp control bit and output to the frequency multiplying unit 92.

The frequency multiplying unit 92 multiplies the lamp driving frequency (60 Hz) by a predetermined multiple to generate a lamp driving frequency of 240 Hz, and then uses the lamp driving frequency at four times every frame. Outputs LED lighting control signal.

10A to 10D show an example in which LEDs are turned on four times in one frame by four times the frequency multiplied by the frequency multiplier 92. Here, FIG. 10 (a) shows that the driving current amounts of each LED are the same, and FIGS. 10 (c)-(d) show that the driving current amounts of each LED are different.

11 illustrates another example in which the LED is turned on four times in one frame by the frequency multiplied by the frequency multiplier 92. In other words, when FIG. 11 illustrates that the LEDs of the LED backlight unit 29 are arranged in a 4 * 4 structure, the frequency multiplier 92 displays the LEDs according to the corresponding output data every cycle within one frame. An example of lighting is shown.

That is, in the first period T1, all 16 LEDs are turned on according to the output data '0000', and in the second period T2, all LEDs except four LEDs out of the 16 LEDs are turned on according to the output data '1100'. In the third cycle (T3), all LEDs except one LED are lit according to the output data '0010', and in the fourth cycle (T4), all the LEDs are lit according to the output data '1110'. Turn on all LEDs except nine LEDs.

Of course, thereafter, the respective LEDs are sequentially turned on over each of four cycles as described above.

Meanwhile, FIG. 12 illustrates another embodiment of the LED driver 28 driving the backlight by using the BRC method and the dithering method by mixing the two embodiments of FIGS. 3 and 9.

Here, the luminance analyzer 121, as in the luminance analyzer 31 of FIG. 3 and the luminance analyzer 91 of FIG. 9, analyzes the luminance of the input image from the timing controller 23. 2 bits of the most significant bit (MSB) of the input data are extracted as the lamp (LED) control bits and output to the lamp lighting controller 122 and the frequency multiplier 123.

In addition, the lamp lighting controller 122 generates 4bit lamp driving data based on the lamp control bit input from the luminance analyzer 121 as the lamp lighting controller 32 of FIG. The lighting of the LEDs on the backlight unit 29 is controlled.

For example, the lamp lighting control unit 122 turns on the LEDs of the T1 periodic sequence of FIG. 12 every frame as in the description of FIG. 8.

In addition, the frequency multiplier 123 generates a lamp driving frequency of 240 Hz by multiplying the lamp driving frequency by four times as in the frequency multiplier 92 of FIG. 9, and then uses the LED four times every frame. Outputs a lighting control signal.

For example, the frequency multiplier 123 outputs an LED lighting control signal for controlling lighting of the corresponding LEDs over four periods T1 to T4 every frame as shown in FIG. 12.

As such, the LED driving unit 28 includes both the lamp lighting control unit 122 and the frequency multiplication unit 123, thereby driving the backlight by simultaneously applying the BRC method and the dithering method.

As described in detail above, the present invention spatially divides the backlight LEDs and lights them in the BRC method, or multiplies the backlight driving frequency to obtain a time-divided driving frequency, and then lights the lamp LEDs by using the dithering technique. By making it possible, the light transmittance can be adjusted, whereby the color depth is increased.

Claims (13)

An LED backlight unit for emitting a backlight by using an LED on the liquid crystal display unit on the liquid crystal panel; A luminance analyzer for extracting a ramp control data bit from the input data to analyze luminance of the input image; Segment the LEDs on the LED backlight unit, and generate the lamp driving data by expanding the lamp control data bits, and output the lamp driving data to the LEDs of the corresponding divided area as lighting control signals every frame. Backlight control device of the liquid crystal display device comprising a configured LED driver. The backlight control apparatus of claim 1, wherein two bits of the Most Significant Bit (MSB) of the input data input from the timing controller are extracted from the lamp control data bit. delete The method of claim 1, wherein the lamp lighting control unit A data distributor which receives the first and second data a and b and branches them to different output terminals and outputs a data selection signal of a predetermined bit; First and second buffers and a first synthesizer for extending the first data a into two bits of data 'aa'; A second synthesizer for extending the second data b into 'b0' of 2 bits; An inverter for inverting the data selection signal of the predetermined bit; A first and gate for selecting the 2 bit data 'aa' using the data selection signal; A second and gate for selecting the 2-bit data 'b0' using the inverted data selection signal; And an oragate configured to synthesize output data of the first and second gates and output extended 4-bit output data 'aab0'. The backlight control apparatus of claim 4, wherein the data selection signal is 4 bits. The backlight control apparatus of claim 1, wherein the lamp lighting control unit is configured to select the predetermined number of space-divided LEDs each frame so as not to overlap each other and output the lighting control signal to them. The backlight control apparatus of claim 1, wherein the lamp lighting control unit is configured to randomly select the spatially divided LEDs every frame and output the lighting control signal thereto. An LED backlight unit for emitting a backlight by using an LED on the liquid crystal display unit on the liquid crystal panel; A luminance analyzer for extracting a ramp control data bit from the input data to analyze luminance of the input image; And an LED driver configured to multiply the original lamp driving frequency by a predetermined multiple, and use the same to multiply the frequency driving unit to output an LED lighting control signal at a corresponding period every frame. The backlight control apparatus of claim 8, wherein the frequency multiplier multiplies the original lamp driving frequency by a multiple of four. 9. The backlight control apparatus of claim 8, wherein the original lamp driving frequency is 60 Hz. The backlight control apparatus of claim 8, wherein the frequency multiplying unit is configured to output a drive current amount different when outputting the lighting control signal to each LED to be lit. An LED backlight unit for emitting a backlight by using an LED on the liquid crystal display unit on the liquid crystal panel; A luminance analyzer for extracting a ramp control data bit from the input data to analyze luminance of the input image; A lamp lighting controller which spatially divides the LEDs on the LED backlight unit, generates lamp driving data corresponding to the lamp control data bits, and outputs a lighting control signal to the LEDs of the divided region every frame; And a frequency multiplying unit multiplying the original lamp driving frequency by a predetermined multiple and outputting an LED lighting control signal at a corresponding period every frame by using the same. The backlight control apparatus of claim 12, wherein the lamp lighting control unit and the frequency multiplication unit are configured to be driven at the same time.

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